Calcium is considered to be one of the most important minerals in the human body. It is required for maintaining bone mass, is essential for exocytosis of neurotransmitters, takes part in the contraction of muscle cells, replaces sodium as the depolarizing mineral in the heart, and participates in many other physiological functions. Calcium is further an important structural element in biological systems. From protozoa to vertebrata, deposited calcium salts helps to keep rigid bodily shapes of animals, calcium phosphate being the main component of endoskeletons in the vertebrates and calcium carbonate of exoskeletons in the invertebrates. Calcium carbonate has six known polymorphs, three of which are anhydrous crystalline (i.e. calcite, aragonite and vaterite) two of which are hydrated (i.e. crystalline monohydrocalcite and ikaite) and one of which is hydrated amorphous namely amorphous calcium carbonate (ACC). The most thermodynamically stable of these forms is calcite, while the least stable is ACC. ACC is a transient polymorph that rapidly crystallizing into one of the five more stable polymorphs. Calcified exoskeletons with calcium carbonate minerals as the main constituents are widespread among echinoderms, mollusks, and arthropods, providing protection and serving as calcium storage. Some crustaceans store calcium carbonate temporarily, in an amorphous state, which makes it better available, particularly for quick mobilization during the mineralization of their new exoskeleton structures after molting. The formation of amorphous calcium carbonate in the living bodies of, for example, crayfish is rather intriguing, since amorphous minerals are usually thermodynamically unstable. Several techniques have been reported for the synthesis and stabilization of ACC, however, all known methods use either toxic materials or various organic polymers to stabilize ACC for more than three days. WO 2005/115414 employs crustacean organs for providing compositions with stable ACC which is readily available for human consumption.
In view of the general metabolic and biomechanical importance of calcium, and since ACC is a potentially more soluble and absorbable form of calcium carbonate as a dietary supplements, it is an object of the invention to provide new methods for preparing amorphous calcium carbonate.
It is another object of this invention to provide pharmaceutical and nutraceutical compositions comprising stable ACC, which exhibit higher solubility and bioavailability compared to crystalline calcium carbonate compositions.
Other objects and advantages of present invention will appear as description proceeds.